It's extremely cumbersome, bureaucracy heavy, slow and expensive. In addition I've never encountered as many scummy companies (GmbH or otherwise) as in Germany. Corporate rules and culture are both complete trash.
For reference I've started companies in Sweden, and I can do the full process online in an afternoon. Probably less than 30 minutes.
If I ever had to have a business for operating in Germany again, I would create an Estonian business. There's no reason that you corporate entity has to be German itself.